- Adapt: organisms become better suited to environmental conditions via heritable (genetic) change over generations.
- There is a ying and yang between the environment and evolution
- complementary forces that interact to form a dynamic system
Evolution by natural selection
Evolution by natural selection
Natural Selection: Differences among individuals in a population in survival and reproduction
Organisms which are better suited to their environment survive and reproduce better, leading to a change in the average traits of a population over time
Evolution by natural selection
Natural Selection: Differences among individuals in a population in survival and reproduction
Fitness: Measure of ability to survive and reproduce
Adaption: A trait that confers an advantage in a particular environment that evolved via natural selection
What did Darwin mean by fitness?
- Best suited for the environment
- biggest? fastest? strongest? smartest?
- He intended “fittest” to mean the members of the species best suited for the immediate environment
- individual needs the most favorable traits to survive in the environment
- environments can change at any time
- Those lacking the favorable traits—the “unfit”—most likely won’t live long enough to pass down their unfavorable traits
- those traits will be breed out of the population
- ‘breeding out’ traits can take a long time
Conditions necessary for natural selection
-
Variation: Individuals in a population vary
- mutation as ultimate source of variation
- migration -> gene flow within species
- introgression -> genetics crosses species boundaries
-
Heredity: Offspring resemble parents
- DNA as primary mechanism of heredity
- If a trait is only environmentally determined, it cannot be adaptive
- Differential survival or reproduction: Not all individuals survive, those with favorable traits survive and reproduce
Ways of studying adaptation (experimental evolution)
Ways of studying adaptation
